1. Field of the Invention
Embodiments of the invention generally relate to the field of pressure regulating valves, and more particularly to pressure regulating valves that are capable of passing high flow rates with minimal droop with low pressure differential across the valve. In addition, embodiments of the invention relate to pressure regulating valves having an automatic downstream overpressure bleed mechanism.
2. Discussion of Related Art
Further, current high flow rate regulating valves are often manufactured from separate diaphragm and pilot regulator valves that are piped or mounted together. A disadvantage of such an arrangement is that it requires the coupling of two separate valves, which increases the total number of components required, as well as the total number of joints and consequently potential leaks. Thus, it would also be desirable to provide a regulator design that incorporates a regulator and a pilot regulator in a single valve.
Further, current high flow regulator valves often have a large main diaphragm to provide desired sensitivity to small pressure differentials and to accommodate a desired flow rate. The larger the diaphragm, the more sensitive the regulator is to small pressure differentials. Thus, in some valves, the main diaphragm may be multiple times greater than the seat diameter. It would be desirable to provide a regulator design that is sensitive to small pressure differentials, but does not require a large main diaphragm.
Further, current pressure regulating valves often have less than desirable droop characteristics. Generally, droop is the deviation of pressure from the set value of a valve as the valve travels from a minimum flow position to a full flow position. It would be desirable to provide a regulator design capable of passing high flow rates with small droop characteristics.
Further, pressure regulating valves are used in industrial applications to respond to various pressure changes within a system. Such valves are often isolated in a piping system by upstream and downstream isolation valves. During system startup, if the downstream side of a pressure regulator is deadheaded and the upstream isolation valve is opened to pressurize the regulator inlet, the regulator's pressure plate can quickly lift, providing a “burp” of high pressure air downstream. A similar “burp” of high pressure air can also be caused by rapid closing of the downstream isolation valve while flowing at high rates. This high pressure “burp” can provide a false sense of what pressure the valve is regulating. In such instances, readings taken from a downstream pressure gauge may give the appearance that the regulator is not set properly, even if no adjustment is actually required.
To combat this problem in current valves, downstream pressure is manually bled off to reduce the outlet pressure to the actual set pressure of the regulator. This manual process, however, can be time consuming, and thus it would be desirable to provide an inexpensive method for automatically bleeding off downstream excess pressure in a regulator valve to avoid the aforementioned problems.